Computer numerically controlled milling machines are used to process (such as edge finishing) sheet type materials of various material composition, shape, and dimensions and are known to also enable sawing operations. In a sawing operation, materials are held in place for processing by some weight bearing supports. The material to be cut cannot be supported directly from an unprotected table surface as the saw blade needs to cut to a depth slightly below the bottom depth of the slab of material in order to produce a clean cut. This “through material” requirement means that the material must either be supported over a table with a known, cleared path for the blade to pass, or it must be supported on a table having dressed and re-dressable sacrificial material overlying a metal table.
Both of these typical provisions for cutting material are burdensome. In the case where cutting over a known free path is required, the supports must be precisely pre-arranged to avoid cutting through the support structures. One miscalculation can cause the saw blade to strike a support and damage it or the saw blade. In the case of a re-dressable table, operations must stop once the table is scarred to the extent that it is no longer able to evenly support the material to be cut. In addition a dressed table committed to a sawing operation is limited in its other uses.
For tables which are not wholly dedicated to sawing of material, vacuum hold down supports are often used. Vacuum hold down supports using single or double sided vacuum supports positioned on the working surface of the machine are placed strategically beneath the part being processed. The bottom of the vacuum hold down support is independently held by a vacuum to the working table, and an upper vacuum member typically vacuum engages the material to be worked. In the case of vacuum supports, operators who wish to perform sawing operations have been limited to using the known free path method. Further, the placement of the vacuum hold downs to avoid sawing of the vacuum supports will normally not be in the same layout placement of the vacuum supports needed in properly supporting the slabs of material to be edge shaped.
The location and placement of the vacuum hold down supports for general shaping operations is usually dependent upon the size and weight of the material to be processed, and the type of processing which is to occur. General processing can occur with a computer numerical controlled (CNC) machine which has a spindle on which is mounted various grinding tools. CNC machines used in the stone, glass and wood industry have attachments that permit sawing of material by transferring rotational power from the vertical axis to the horizontal axis to then enable computer controlled precision guided sawing at any height and axis of rotation. The material to be sawed is typically a large thick slab of material, 2 cm, 3 cm, 4 cm, thickness and has significant weight (with the 2 cm material weighing approximately fourteen pounds per square foot and other thicknesses weighing proportionately more. This material can be granite, marble or other hard material which must be well supported and sawn completely through while maintaining adequately support until the cut is completed. When vacuum supports are used, the cutting pattern must be exactly known in advance in order to configure the cups to avoid being cut by the saw blade. Even one vacuum hold down which is improperly placed, or even one cutting error can cause severe and costly damage. Further, since most vacuum hold down devices are placed in a pattern manually, the additional requirement that the vacuum hold down devices be precisely placed will at minimum cause the setting of the vacuum supports in two configurations, a first one for the sawing operation and a second one for the edge processing operation.
Another alternative to the use of a table with a dressed surface specifically configured for sawing, has been use of a large, flat intermediate cutting material supported by vacuum supports. A large size sacrificial board assembly includes a backing made of aluminum having an aluminum thickness of about ¼ inch, and having an overall size corresponding to the size of slab material to be cut. This type of sacrificial board assembly is heavy and requires two or more workers to handle it effectively. The aluminum backed material is put into place over suction cups and then vacuumed to hold it in place. This enables less concern on where the vacuum cups are located, but has a number of disadvantages. This large piece can be very expensive, difficult to handle, and is easily damaged. Once damaged this large piece of material must be replaced at a significant cost.
What is needed is a system which enables an existing CNC machine to be used for sawing so that CNC users do not have to invest in a separate sawing machine. Conversely, a dedicated sawing machine needs to have freedom from requiring a dressable support surface so that it can utilize vacuum hold down supports. The needed system enables slab material on a CNC working table to be adequately supported, while maintaining the minimum necessary friction between the slab of material being cut and its support structure to insure that it will not shift. The needed system should both insure a good, stable, non-shifting support, while completely eliminating any damage to a permanent support structure, such as a vacuum hold down.